A novel vanadium(IV) phosphate V III V IV 3 O 3 (PO 4 ) 3 has been synthesized and crystallized (1073 K, sealed silica tube, a few milligrams of PtCl 2 as mineralizer). According to the single-crystal structure analysis [orthorhombic, F2dd (No. 63), Z ) 24, a ) 7.2596(8) Å, b ) 21.786(2) Å, c ) 38.904(4) Å (lattice parameters from Guinier photographs), R 1 ) 0.032, wR 2 ) 0.067, κ-CCD diffractometer, 83 949 reflections measured, 6836 independent, 5986 with I > 2σ(I), 299 variables], V III V IV 3 O 3 (PO 4 ) 3 belongs to the Lipscombite/Lazulite structure family. At 1073 K V III V IV 3 O 3 (PO 4 ) 3 is in thermodynamic equilibrium with (VO) 2 P 2 O 7 , VO 2 , and VPO 4 . Substitution of V 3+ in V III V IV 3 O 3 (PO 4 ) 3 by Cr 3+ and Fe 3+ is possible. Like vanadylpyrophosphate the oxide phosphates M III V IV 3 O 3 (PO 4 ) 3 (M III : V, Cr, Fe) show significant catalytic activity in selective oxidation of n-butane and 1-butene to maleic acid anhydride.

Emerald-green single crystals of U(PO4)Cl were grown by chemical vapor transport in a temperature gradient (1000 → 900 °C). The crystal structure of U(PO4)Cl (Cmcm, Z = 4, a = 5.2289(7) Å, b = 11.709(2) Å, c = 6.9991(8) Å) consists of a three-dimensional network of [PO4] tetrahedra and bicapped octahedral [U(IV)O6Cl2] groups. Polarized absorption spectra measured for two perpendicular polarization directions show a large number of well-resolved electronic transitions. These transitions can be fully assigned on the basis of a detailed ligand-field treatment within the framework of the angular overlap model. The magnetic behavior predicted on the basis of the spectroscopic data is in agreement with an f (2) system and perfectly matched by the results of temperature-dependent susceptibility measurements.

Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(P±O) = 0.004 A Ê Disorder in solvent or counterion R factor = 0.027 wR factor = 0.059 Data-to-parameter ratio = 15.2 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. # 2004 International Union of Crystallography Printed in Great Britain ± all rights reserved Langbeinite-type Ba 3 V 4 (PO 4 ) 6 has been crystallized from a stoichiometric melt starting from Ba(PO 3 ) 2 and V 2 O 3 . The crystal structure has been re®ned from single-crystal X-ray diffraction data. It consists of a vanadato(III)±phosphate network [V 4 (PO 4 ) 6 ] 6À , which shows some resemblance to the NASICON structure type. A new method is presented for the visualization of this structural relationship. The single-crystal electronic spectrum of yellow±green Ba 3 V 4 (PO 4 ) 6 shows the absorption bands typical for the octahedral chromophore [V III O 6 ]. CommentQuaternary diphosphates AM II P 2 O 7 (A: Ca, Sr, Ba; M II : Mg, Cr±Zn) allow stabilization of transition metals in compara-

Emerald‐green single crystals of U(PO4)Cl are prepared by chemical vapor transport in a temperature gradient of 1000 → 900 °C from a stoichiometric mixture of UP2O7, UO2, and ZrCl4.

No abstract